The present invention generally relates to an apparatus and a method for testing the property of a fabric and more particularly, relates to an apparatus and a method for testing the air permeability of a fabric by using a quantitative tube filled with a soap solution.
In the recent development of semiconductor fabrication technology, the continuous miniaturization device fabricated demands more astringent requirements in the fabrication environment and contamination control. When the feature size was in the 2 xcexcm range a cleanliness class of 100xcx9c1,000 (i.e., the number of particles at sizes larger than 0.5 xcexcm per cubic foot) was sufficient. However, when the feature size is reduces 0.25 xcexcm, a cleanliness class of 0.1 becomes necessary.
It has been proposed that an inert mini-environment may be the solution to future fabrication technologies when the device size is further reduced. In order to eliminate micro-contamination and to reduce native oxide growth on silicon surfaces, the wafer processing and the loading/unloading procedures of a process tool must be enclosed in a extremely high cleanliness mini-environment that is constantly flushed with ultra pure nitrogen that no oxygen or moisture.
Different approaches in modern clean room design has been pursued in recent years in the advent of the ULSI technology. One is the utilization of a tunnel concept in which a corridor separates the process area from the service area in order to achieve a high level of air cleanliness. Under the concept, the majority of equipment maintenance functions are conducted in low-classified service areas, while the wafers are handled and processed in more costly high-classified tunnels. For instance, in a process for 16 M and 64 M DRAM products, the requirements of contamination control in a process environment is so stringent that the control of the enclosure of the process environment for each process tool must be considered. In order to maintain the high cleanliness class required, the loading and unloading of the process tool must handled automatically by an input/output device such as a SMIF apparatus. The clothing of the machine operator must also be stringently cleaned without introducing particle contaminations into the clean room.
The continuous monitoring of particles, temperature and humidity conditions inside a clean room is required for alerting engineers to changes occurring in the clean room environment such that steps may be taken to prevent particle-sensitive fabrication processes from drifting out of control. The proper gowning procedure and clean room maintenance practices are both critical to prevent any possible micro-contamination in the clean room.
It has long been recognized that the human operators are major sources of clean room contaminants. For instance, not only the operators generate a large number of contaminants, the operators are also in close proximity to the wafers at many different stages of the fabrication process. As a result, a proper gowning procedure becomes critical in minimizing the exposure of human hair, bare skin and contaminants carried on street clothes.
To minimize human contamination, it has been a practice in IC fabrication facilities to require its clean room operators to change from street clothes and street shoes into company-provided clean room suit, a face mask and booties over the street shoes. These clean room suits, masks and booties are worn on the outside of street clothes of clean room operators in a designated area immediately adjacent to a clean room normally known as a gowning room.
A good clean room suit material is normally made of woven fabrics that consist of long synthetic fibers covered with a layer of low friction polymeric material. The polymeric coating material prevents particles from passing through while at the same time allows vapor transmission. The clean room suits and booties are washed regularly using deionized water and sodium-free detergent. Stringent procedures must be followed in providing laundry services to the suits and booties in order to minimize contamination while washing, packaging, transporting, and storing these clean room garments.
A good clean room suit material also requires good breathability or air permeability such that the suit can be worn comfortably by a clean room operator. While the air permeability quality is important, it must be balanced by the possible emission of particles from the human body. For instance, the air permeability must not be so high that the particle counts from a human body increases. The air permeability property of a clean room suit material must therefore be limited by the particle emission property and thus, must be controlled within a suitable range.
Traditionally, the air permeability property of a fabric material is tested by a differential pressure technique in which the pressure difference in two chambers that are separated by a piece of fabric are determined. However, such determination requires specialized equipment for pressurizing the chambers and for making sensitive measurements of a pressure change. The test can not be easily conducted in a factory environment and furthermore, the test apparatus cannot be easily mobilized.
It is therefore an object of the present invention to provide an apparatus for testing the air permeability of a fabric that does not have the drawbacks or shortcomings of the conventional methods.
It is another object of the present invention to provide an apparatus for testing the air permeability of a fabric which can be easily used in a factory environment.
It is a further object of the present invention to provide an apparatus for testing the air permeability of a fabric which can be easily assembled by components that are readily available.
It is another further object of the present invention to provide an apparatus for testing the air permeability of a fabric by using a flow regulator, a flow meter, a sample holder and a quantitative tube.
It is still another object of the present invention to provide an apparatus for testing air permeability of a fabric by utilizing a quantitative tube in which a water solution of soap is utilized to generate bubbles.
It is yet another object of the present invention to provide a method for testing air permeability of a fabric by utilizing a simple arrangement of a test apparatus.
It is still another further object of the present invention to provide a method for testing air permeability of a fabric by utilizing a quantitative tube and determining the amount of time for a soap bubble to travel through the tube.
In accordance with the present invention, an apparatus and a method for testing air permeability of a fabric are provided.
In a preferred embodiment, an apparatus for testing the air permeability of a fabric can be provided which includes a flow regulator for controlling the flow rate of an air flow therethrough; a flow meter in fluid communication with the flow regulator for indicating an air flow rate; a sample holder in fluid communication with the flow meter for holding a fabric sample therein such that the air flow passes through the fabric sample exiting an outlet tube; and a quantitative tube equipped with an arch portion that is optically transparent in fluid communication with a gas outlet on top of the quantitative tube and a fluid reservoir at a bottom of the quantitative tube, the fluid reservoir for holding a quantity of a fluid that generates bubbles when air passes over a top surface of the fluid and is connected to the enlarged portion by a tube section, the tube section is further in fluid communication with the outlet tube of the sample holder for admitting the air flow flown through the fabric sample and for exiting the air flow from the gas outlet on top.
The apparatus for testing the air permeability of a fabric may further include a shut-off valve situated upstream of the flow regulator for turning on or off the air flow. The sample holder may be formed in a cylindrical tube that holds a fabric sample under a hollow cap at one end of the cylindrical tube, the sample holder may also be a cylindrical tube that is formed of a plastic material and provided with a plurality of vent holes for buffering the air flow passing through the fabric sample. The apparatus may further include plastic tubing means providing fluid communication in-between the flow regulator, the flow meter, the sample holder and the quantitative tube. The quantitative tube may be formed of glass, the flow meter may be of the gravity ball type. The sample holder may be a PVC tube that has a plurality of apertures drilled therethrough. The quantity of fluid that generates bubbles when air passes over a top surface of the fluid may be a water solution of soap. The flow regulator may be a butterfly valve. The enlarged portion of the quantitative tube is provided with a lower mark and an upper mark at two extreme ends of the enlarged portion.
The present invention is further directed to a method for testing air permeability of a fabric which can be carried out by the operating steps of first providing a flow regulator, a flow meter, a sample holder and a quantitative tube that are in fluid communication with each other, then flowing an air flow through the flow regulator, the flow meter, the sample holder and a fabric sample such that a bubble is generated from a quantity of fluid kept in the quantitative tube and observing the bubble rising up through a lower mark and an upper mark in the quantitative tube; and then counting the time required for the bubble to pass from the lower mark to the upper mark as an indication of the air permeability of the fabric sample.
In the method for testing air permeability of a fabric, the sample holder may be a PVC tube that has a plurality of ventilation holes therethrough, the sample holder may be a cylindrical tube that has a diameter of about 1 cm, the enlarged portion of the quantitative tube may have a volume of about 90 cm3 between the lower mark and the upper mark such that a relative air permeability can be calculated by an equation of 90/(number of seconds for bubble to rise) (cross-sectional area of sample tube). The method may further include the step of providing a shut-off valve that is situated upstream of the flow regulator for turning on or off the air flow. The method may further include the step of buffering the air flow by the plurality of vent holes provided through the sample holder tube. The method may further include the step of connecting the flow regulator, the flow meter, the sample holder and the quantitative tube in fluid communication by PVC tubes, or the step of generating a bubble from the quantity of fluid prepared by dissolving soap in water.